Mitsuji Hirata

The Interactions of Point Defects with Impurities in Silicon

The minority carrier lifetime in gamma-irradiated silicon crystals was studied. In F. Z. n type crystals containing phosphorous, arsenic, antimony or bismuth, there are two annealing stages in the temperature range 100–280°C and in both stages there is strong dependency of activation energies E a and frequency factors on the atomic size of the impurity. The relationship between E a and covalent radii of the impurity atom can be experimentally expressed in linear functions. The defect which anneals in the lower temperature stage is a complex of donor atoms associated with a vacancy type defect. Si-E center anneals in the higher temperature stage and the values of activation energies completely agree with those obtained by Watkins et al. in their experiments of reorientation of donor-vacancy axis. The defects of both stages are considered to migrate to the sinks of oxygen after jumps of about 10 5 . It is very interesting to note that this study shows only one example of an impurity atom which moves with a ...

EFFECT OF IMPURITIES ON THE ANNEALING BEHAVIOR OF IRRADIATED SILICON.

The effect of impurities on the annealing behavior of irradiated silicon was studied through an investigation of isothermal annealing of minority carrier lifetime in silicon crystals containing phosphorus, arsenic, antimony, or bismuth in the temperature range 100°–180°C. The activation energy for the annealing of vacancy‐impurity complex increased with increasing atom size of the dopant. The values are 0.93, 1.27, 1.84, and 2.22 eV. The frequency factor was also found to be dependent on impurity as well as concentration of the complex. The variation of these parameters is discussed in terms of the lattice strain associated with impurity atoms which have a larger covalent radius than silicon.

Hydrogen-induced platelets in silicon studied by transmission electron microscopy

Abstract The structure of hydrogen-induced platelets (HIPs) in silicon has been examined with conventional transmission electron microscopy (CTEM) and high-resolution transmission electron microscopy (HRTEM). Hrtem was utilized to clarify the atomic structure in which hydrogen atoms are assumed to saturate the broken bonds between adjacent (111) planes. The structural model was refined by introducing a reliability factor in real space for quantitative comparison between experimental and simulated images. Some contrast variations in HRTEM images can be well explained by allowing for atomic ledges on the (111) plane with broken bonds. Furthermore it is found from the strain contrast in a CTEM image that a considerable amount of H2 gas is contained in the open space of the HIP, which results in an internal pressure as large as 1 GPa. The formation process of Hips is discussed.

Crystallization of Amorphous Si and Ge Whiskers

Crystallization processes of amorphous Si (a-Si) and Ge (a-Ge) whiskers have been investigated by using differential thermal analysis (DTA) and X-ray diffraction. On the crystallization of the a-Si and a-Ge whiskers, the DTA peak temperature is 907 and 527°C at a heating rate of 20°C/min, the activation energy is about 5 and 2.3 eV, and the exothermic heat is about 4 and 3 kcal/mol, respectively. It is found that the energy difference between the amorphous and crystalline states is much smaller than the energy barrier for the crystallization in both cases of Si and Ge. Furthermore, from the observations on the crystallization of amorphous films, it can be concluded that the a-Si whisker is more stable than other amorphous semiconductor films.

HRTEM observation of electron-irradiation-induced defects penetrating through a thin foil of germanium

Abstract The structure of defects introduced in germanium under 2 MeV electron irradiation was studied by means of electron diffraction and high-resolution electron microscopy. It has been observed that the {111} stacking fault of vacancy type interacts with the rodlike defect with hexagonal structure. The (113) defect of interstitial type exhibits similar electron diffraction patterns and high-resolution electron image to those in Si. An analysis of HRTEM images shows that the defect structure on (113) in Ge is isomorphous to that in Si. The density of interstitial atoms in the (113) defect is estimated at 0.65×/√11 a 2 , where a is a lattice parameter of Ge. Self-interstitial atoms are located at lattice points on the extra two sheets of the (113) net plane and constitute interstitial-atom chains in the [1-0] direction. It is revealed that nearly 35% of the lattice points are systematically unoccupied to form “vacancy” chains in the same direction. Thus, the interstitial and “vacancy” chains are arranged in short-range correlation.

Structure of planar aggregates of si in heavily si-doped gaas

Abstract Planar defects on {111} planes in heavily Si-doped boat-grown GaAs crystals have been studied with a high-resolution technique in transmission electron microscopy and energy-dispersive X-ray analysis. There are two sizes of defect, both of which are considered to be Si aggregates, precipitated in a GaAs matrix and forming interstitial-type stacking faults. The Burgers vector of the defects are of (a/3) , the same as that of an extrinsic Frank loop. The larger loops form triangles with such orientations as to constitute the surfaces of a tetrahedron. This effect is discussed by considering the type of partial dislocations around the defect.

Characteristics of Whisker Growth in Amorphous Silicon

The growth of amorphous silicon whiskers grown by thermal decomposition of silane (SiH4) in the temperature range between 500 and 800°C in an argon atmosphere has been investigated in detail. A thin gold film (about 200 A) on the substrate seems to act as the most effective catalyzer for the whisker growth. The time rate of axial growth at the beginning of each growth curve seems to be proportional to the partial pressure of SiH4. Radial growth proceeds at a constant rate and remains constant even after termination of the extension in length. The two mechanisms of elongation and thickening are controlled by independent activation processes whose activation energies are 0.73 eV and 2.1 eV respectively.

Structure of hydrogen‐induced planar defect in silicon by high‐resolution electron microscopy

It has been known that introduction of hydrogen into silicon at moderate temperatures results in extended planar defects on {111} planes. The structure of the hydrogen‐induced defects in silicon has been investigated by means of high‐resolution transmission electron microscopy. As a result of the contrast analysis of the high‐resolution images, with the aid of computer simulation, we propose a new structural model, which involves breaking of Si—Si bonds between layers of smaller spacing, connected with three bonds per atom, rather than those of larger spacing with one bond per atom. The broken bonds are considered to be saturated by hydrogen atoms.

Transmission Electron Diffraction Pattern of Electron-Irradiation-Induced {113}-Faulted Loops in Si

Transmission electron diffraction patterns from {113}-faulted loops in Si, which are introduced by electron irradiation in a high-voltage electron microscope, have been observed for the first time. The diffraction patterns were observed after removing the perfect crystal of Si by ion-thinning. The patterns were taken under the plan-view condition. The patterns were consistently interpreted by assuming a 1×1 unit cell on a {113} plane.

Visual Observation of Whisker Growth in Amorphous Silicon

Amorphous silicon whiskers have been grown in an atmosphere composed of SiH 4 (5%) and argon (95%) at around 650°C. Time-lapse sequence of the growth of whiskers is presented in this report. By using an optical system, it has been observed that the growth proceeds at their tips.